Quantitative Assessment of Hyaline Cartilage
Elasticity during Optical Clearing using
Optical Coherence Elastography
Chih-Hao Liu1, Manmohan Singh1, Jiasong Li1, Zhaolong Han1, Chen Wu1, Shang Wang2, Rita Idugboe1, Raksha
Raghunathan1, Valery P. Zakharov3, Emil N. Sobol4, Valery V. Tuchin3,5,6, Michael Twa7, and Kirill V. Larin1,3,5,6+
1Department
2Department
of Biomedical Engineering, University of Houston, 3605 Cullen Boulevard, Houston, Texas 77204 USA
of Molecular Physiology and Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, Texas, 77030 USA
3Department
of Electrical Engineering, Samara State Aerospace University, Samara, 443086 Russia
4Department
5Department
of Optics and Biophotonics, Saratov State University, Saratov, 410012 Russia
6Interdisciplinary
7College
of Physics, Moscow State University, Moscow, 119991 Russia
Laboratory of Biophotonics, Tomsk State University, Tomsk 634050 Russia
of Optometry, University of Houston, 505 J.Davis Armistead Bldg., Texas 77204 USA
+
Corresponding author: klarin@uh.edu
Motivation
Laser septochondrcorrection (LSC)
(non-destructive surgery)
• advantage
• Safe(bloodless, painless)
• non-invasive
• Less complication compared with
traditional septoplasty surgery [1,2]
Fig: Scheme of Laser septochondrcorrection procedure
• Stress relaxation process
• Permanent deformation
• Change from Bound water to free
water state
Biomechanical
property changes [3]
Fig: Optimal condition for laser reshaping window [3]
Fig: Stress relaxation mechanism [4]
[1] M. G. Stewart, T. L. Smith, E. M. Weaver et al., “Outcomes after nasal septoplasty: results from the Nasal Obstruction Septoplasty Effectiveness (NOSE)
study,” Otolaryngology--Head and Neck Surgery, 130(3), 283-290 (2004).
[2] E. Sobol, A. Sviridov, V. Svistushkin et al., "Feedback controlled laser system for safe and efficient reshaping of nasal cartilage." 7548, 75482H-75482H-5.
[3] E. Sobol, A. Sviridov, A. Omel’chenko et al., “Laser reshaping of cartilage,” Biotechnology and Genetic Engineering Reviews, 17(1), 553-578 (2000).
[4] D. E. Protsenko, A. Zemek, and B. J. F. Wong, “Temperature dependent change in equilibrium elastic modulus after thermally induced stress relaxation in
porcine septal cartilage,” Lasers in Surgery and Medicine, 40(3), 202-210 (2008).
Motivation
• Optical clearing technique
• An approach to monitor the change of tissue
optical properties (structural information)
• OCT signal slope [1]
• However…The elasticity changes of biological tissues
during clearing process haven’t been studied yet
• Optical coherence elastography (OCE)
• Biomechanical property measurement
• Cornea[2], soft-tissue tumor[3], cardiac muscle[4]
Fig. Visualization of the elastic wave propagation in ex vivo rabbit cornea
• In this work
• we report the first use of OCE to monitor the
elasticity changes during optical clearing process.
• Speckle variance analysis
• OCE detection
• Uniaxial mechanical testing
[1] K. V. Larin, M. G. Ghosn, A. N. Bashkatov et al., “Optical clearing for OCT image enhancement and in-depth monitoring of molecular diffusion,” IEEE Journal of
Selected Topics in Quantum Electronics, 18(3), 1244-1259 (2012).
[2] S. Wang, and K. V. Larin, “Shear wave imaging optical coherence tomography (SWI-OCT) for ocular tissue biomechanics,” Optics letters, 39(1), 41-44 (2014).
[3] S. Wang, J. Li, R. K. Manapuram et al., “Noncontact measurement of elasticity for the detection of soft-tissue tumors using phase-sensitive optical coherence
tomography combined with a focused air-puff system,” Optics letters, 37(24), 5184-5186 (2012).
[4] S. Wang, A. L. Lopez, Y. Morikawa et al., “Noncontact quantitative biomechanical characterization of cardiac muscle using shear wave imaging optical
coherence tomography,” Biomedical Optics Express, 5(7), 1980-1992 (2014).
Material and method
• Sample preparation
• Two samples were width-wise extracted from the same nasal septum
cartilage
• OCE measurement
• Uniaxial mechanical testing
1.3cm
• Optical clearing agent
• 1X PBS
• 20% glucose
• Clearing period
• 0-20 min: 1X PBS
• 21-140 min: 20% glucose
1cm
Fig: The used cartilages during the optical clear experiment
Phase-stabilized swept source OCT (PhS-SSOCT)
•
•
•
•
•
•
•
Broad band swept laser:1310nm
Scan range: 150nm
Scan rate: 30k Hz
The axial resolution: ~11 µm
Phase stability: 16 µm
Scan distance: 6.25mm (n=251)
OCT signal
• Phase: Elastic wave velocity
• Intensity: Speckle variance
• Uniaxial mechanical compression testing
Fig: diagram of mechanical compression testing
Fig: Schematic diagram of PhS-SSOCT
Quantification of elasticity from OCE
• Displacement profile
d ( x, t ) 
0
[I ( x, t ) x  2 nx  I ( x, t0 ) x  2 nx ]
4 n
Where λ0 was the central wavelength of the laser
source, and ÐI(x,t) was the phase of OCT signal, and n
was the refractive index.
• Elasticity quantification:
Fig: (left) OCE setup with OCE measurement positions. (left) typical displacement profile
Corresponding to the red point in (left)
• Time delay t
• Cross-correlation analysis
d
• Elastic group Velocity can be expressed as: Cg 
3
t
• Young’s modulus [1]: E  2 (1  v) Cg 2
(0.87  1.12v)2
where ρ=1100 kg/m3 was the density of the tissue, ν=0.5 was the Poisson ratio
[1] Shang Wang, J. Li, S. Vantipalli et al., “A focused air-pulse system for optical-coherence-tomography-based measurements of tissue elasticity,” Opt. Lett., 10(7), (2013).
Speckle variance computation
• Speckle variance [1]
• Study the fluid kinetics during
the clearing process
• Procedure
• Perform a linear fit on the OCT Aline signal
• The linear fit was then
subtracted from the OCT signal
• The speckle variance was
determined by a standard
deviation of the slope removed
OCT signal
Fig: (left) A typical OCT A-line intensity profile with a linear fit (right) Slope-removed
OCT A-line intensity profile with standard deviation bounds.
[1]C.-H. Liu, J. Qi, J. Lu et al., “Improvement of tissue analysis and classification using optical coherence tomography combined with Raman spectroscopy,” Journal of Innovative Optical Health Sciences, 8(2), 1550006 (2014).
Result
• Speckle variance
• Kinetic glucose
diffusion
• 50-140 min
• OCE elasticity
• 0-20 min
(water absorbance)
• 20-30min
(Bound to free water
state)
• 30-140min
(water diffused back)
Fig: Stress relaxation mechanism [1]
Fig: (upper) Speckle variance, as quantified by the standard deviation of the slope-removed A-line intensity
profile. (lower) Young’s modulus as estimated by equation (2) utilizing the elastic wave group velocity as
measured by PhS-SSOCE. The cartilage sample was immersed in 1X PBS for 20min, then in 20% glucose for
120min.
[1] E. Sobol, A. Sviridov, A. Omel’chenko et al., “Laser reshaping of cartilage,” Biotechnology and Genetic Engineering Reviews, 17(1), 553-578 (2000).
Result
• Quantitative value
difference
• Anisotropy of the
biomedical properties [1]
Fig. (upper) Elasticity as measured by PhS-SSOCE and uniaxial mechanical testing. (lower) Uniaxial
mechanical compression testing. The cartilage sample was immersed in 1X PBS for 20 minutes, then in 20%
glucose for 120 minutes.
[1] B. J. F. Wong, K. K. H. Chao, H. K. Kim et al., “The Porcine and Lagomorph Septal Cartilages: Models for
Tissue Engineering and Morphologic Cartilage Research,” American Journal of Rhinology, 15(2), 109-116 (2001).
Conclusion
• The elasticity of the cartilage
• Decrease
• Sample dehydration caused by glucose solution.
• Increase
• Sample hydration by the water diffused back to the cartilage during mechanical compression
test
• The elasticity trend obtained by
• PhS-SSOCE
• uniaxial compression test
are in agreement
• The results demonstrate the feasibility of utilizing OCE to detect and monitor the
biomechanical properties during optical clearing.
• In Future,
• Viscosity change
characterize the water content of the cartilage.
Lab members
Questions?